46 results about "Gas pressure sintering" patented technology

The invention relates to the technical field of high-performance structural ceramic materials and corrosion resistance optimization thereof, in particular to a preparation method of high-performance silicon nitride ceramic, which realizes performance improvement through dynamic optimization of a composite sintering aid, closed-loop regulation and control of air pressure sintering and multi-process data linkage. In the raw material pretreatment stage, a laser particle size analyzer is adopted for monitoring particle size distribution in real time, surface modification parameters are adjusted in a linkage mode, and a uniform monomolecular coating layer is formed; the proportion of rare earth oxide and aluminum oxide in the composite sintering aid is dynamically adjusted according to the fluctuation of the mixing torque, and agglomeration and segregation of the aid are inhibited. And in the air pressure sintering stage, the argon pressure and the heating rate are dynamically adjusted based on the slope of a shrinkage curve, and directional arrangement of beta-phase grains is promoted by combining low-temperature nitrogen protection and high-temperature argon densification. And multi-dimensional process control synergistically optimizes grain boundary components, structure and density, so that the corrosion resistance and the service life of the silicon nitride ceramic in a sulfur-containing environment are remarkably improved and the service life of the silicon nitride ceramic in the sulfur-containing environment is remarkably prolonged.

The invention provides a method for preparing a high-performance silicon nitride ceramic ball based on a pressure modulation sintering technology, and relates to the field of functional ceramic material preparation, and the method comprises the following steps: 1, preparing a green body; 2, PMS sintering is carried out; step 3, cooling; traditional high-performance silicon nitride ceramic balls (the relative density is required to be larger than 99%, the Vickers hardness is required to be larger than or equal to 1500 kgf / mm, the bending strength is required to be larger than or equal to 920 MPa, and the fracture toughness is required to be larger than or equal to 6.0 MPa.m / ) are mainly prepared through a two-step process of normal pressure / air pressure sintering (GPS) and hot isostatic pressing (HIP). Although high densification of the material can be realized, the method has the problems of complicated process flow, high energy consumption, long production period, high equipment occupancy rate and the like.

The invention discloses ceramic containing an air cooling structure and a preparation method and application thereof. The method comprises the following steps: uniformly mixing a sintering aid and ceramic powder, embedding the mixture into a template for pre-pressing molding, sintering at high temperature, and removing the template by adopting a high-temperature oxidation method (800-1000 DEG C, 1-3 hours) combined with a sand blasting auxiliary method (the sand blasting pressure is 0.2-0.8 MPa, and the sand blasting time is 1-5 minutes) to form a through air cooling channel; for ceramic powder easy to react with the template, spraying a boron nitride coating of 5-20 microns on the surface of the template to prevent interface reaction; various sintering modes (such as air pressure sintering and spark plasma sintering) and template shapes (such as a straight-through type and a spiral type) are supported, the structural controllability is good, channels are removed cleanly, and the process is simple; the obtained ceramic has excellent thermal management capability while maintaining high density and mechanical properties, and is suitable for high thermal load environments such as hot end parts of aerospace engines and the like.

The invention discloses a preparation method of high-purity aluminum nitride single crystal powder. The method comprises the following steps: uniformly mixing raw materials aluminum powder and aluminum nitride powder according to a ratio, putting the mixture into an air pressure sintering furnace, vacuumizing, introducing high-pressure argon, heating to a set temperature, introducing nitrogen, carrying out a fire blast reaction, cooling to room temperature, and crushing to obtain the high-purity aluminum nitride single crystal powder with D50 of 20-200 microns. According to the method, the synthesis of the coarse-particle high-purity aluminum nitride single crystal powder is realized by utilizing the rapid nitridation explosion reaction of the aluminum powder in the high-temperature and high-pressure nitrogen, the method has the characteristics of simple process and low preparation cost, and the prepared high-purity aluminum nitride single crystal powder can be used as a high-thermal-conductivity filler for electronic packaging.

The invention belongs to the technical field of electronic ceramic substrate materials, and particularly relates to a preparation method of a microcrystalline glass composite silicon nitride ceramic substrate, which is prepared from the following raw materials: 1-5% of alpha-phase silicon nitride powder, 86-95% of beta-phase silicon nitride powder, 0.2-3% of metal silicon powder, 2.5-8% of glass powder and 1.3-8% of metal oxide. The preparation method comprises the following steps: S1, mixing and grinding raw materials to obtain ceramic slurry; s2, adding Arabic gum into the ceramic slurry as a binder, and carrying out spray granulation; granulation powder is obtained; s3, carrying out dry pressing molding and cold isostatic pressing treatment on the granulation powder to prepare a ceramic plate blank; and S4, sintering and crystallizing the ceramic plate blank. According to the invention, the glass ceramic powder is introduced as a sintering aid and a second phase, and the sintering temperature of the silicon nitride is obviously reduced from the conventional temperature of more than 1800 DEG C to 1500 DEG C by utilizing the liquid phase effect of the glass ceramic powder in the sintering process, so that two modes of air pressure sintering and normal pressure sintering can be used, and the energy consumption and the requirements on equipment are reduced.

The invention discloses a silicon nitride ceramic formula and a preparation process of a bearing roller matched with the silicon nitride ceramic formula, belongs to the technical field of ceramic materials, and aims to solve the problem of rolling contact fatigue failure caused by insufficient fracture toughness and microscopic crack propagation of an existing silicon nitride bearing roller under high-speed and heavy-load working conditions. The core formula of the invention comprises an alpha-Si3N4 matrix, a composite rare earth additive, a nano TiC modifier and an MgO heat conduction enhancer. The fracture toughness and fatigue resistance of the material are remarkably improved through process nano powder ultrasonic pre-dispersion, closed nitrogen circulation spray granulation, two-step air pressure sintering and cryogenic-thermal tempering gradient stress treatment.

The application discloses a low-temperature normal-pressure sintering preparation method of silicon nitride ceramic for high-power electrothermal elements, and comprises the following steps: (1) mixing silicon nitride powder and nitride glass sintering additives, wherein the amount of the silicon nitride powder is 60%-93% based on the total weight of the mixed raw materials, and the amount of the nitride glass sintering additives is 7%-40%; (2) drying the mixture obtained in the step (1) to obtain dry materials; (3) forming the dry materials obtained in the step (2) to obtain formed materials; and (4) sintering the formed materials obtained in the step (3) under normal pressure. According to the method, the sintering temperature is reduced to a low-temperature interval of 1550-1680 DEG C by using the nitride glass sintering additives, the dependence on expensive and complex hot-pressing or gas-pressure sintering equipment is eliminated, the normal-pressure sintering of high-performance silicon nitride ceramic is realized while the energy consumption and cost are significantly reduced, and a process foundation is laid for large-scale and low-cost manufacturing.

The invention relates to a long-column-shaped beta-Si3N4 crystal grain controllable growth ceramic ball material and a preparation method of the long-column-shaped beta-Si3N4 crystal grain controllable growth ceramic ball material. The material is prepared by taking alpha-Si3N4 powder as a matrix and adding beta-Si3N4 seed crystal and a composite sintering aid in a specific proportion through a multi-stage air pressure sintering process. The formula comprises the following components in parts by weight: 80-95 parts of alpha-Si3N4 powder, 1-20 parts of beta-Si3N4 seed crystal and 3-10 parts of a composite sintering aid, wherein the composite sintering aid consists of R2O3 (R is at least one of Y, Ce and Lu) and Al2O3. Through seed crystal induction and sintering process control, controllable growth of the size, the length-diameter ratio and the spatial distribution of long columnar beta-Si3N4 crystal grains in the ceramic ball is realized, and the prepared silicon nitride ceramic ball has excellent performances of high toughness, high strength, long service life and the like; and the method is suitable for high-end equipment fields such as high-speed bearings, precision machine tools and wind power generation equipment.

The present invention discloses a novel rotary pneumatic sintering furnace, comprising a furnace body, an inner liner, a furnace cover, a locking cover screw and a locking cover nut. Support seats are respectively provided at the left and right ends of the bottom of the furnace body. The inner liner is provided inside the furnace body. A partition is welded to the left end of the inner liner, and the partition is fixedly connected to the inner wall of the furnace body. The furnace cover is rotatably installed on the right end of the furnace body. The groove provided at the bottom of the furnace cover is movably clamped on the outside of the locking cover screw provided at the bottom right side of the furnace body. The right end of the locking cover screw is threadedly installed with a locking cover nut. A connecting pipe is provided at the top left end of the furnace body. The novel rotary pneumatic sintering furnace can realize the simultaneous firing of multiple batches of ceramic blanks, and by driving the rotary furnace frame to rotate, the ceramic blanks placed in the discharge rack can be evenly heated. At the same time, the ceramic blanks can be moved by changing their positions, which is conducive to obtaining ceramic products with more uniform structure and performance.

This invention belongs to the field of ceramic materials technology, specifically relating to photocurable silicon nitride ceramic slurry, silicon nitride ceramics, and their preparation methods. The invention involves sequentially subjecting silicon nitride powder to surface oxidation modification and sintering aid coating modification to obtain a silicon nitride composite powder with a silicon nitride core, a silicon dioxide intermediate layer, and a sintering aid outer shell. This composite powder is then uniformly mixed with a photocurable resin, a photoinitiator, and a dispersant to prepare a photocurable silicon nitride ceramic slurry. The slurry is then photocured and 3D printed to obtain a silicon nitride ceramic green body, which is subsequently subjected to thermal debinding and pressure sintering to obtain the photocurable silicon nitride ceramic. This invention, through two-step chemical modification, simultaneously optimizes the optical properties and sintering activity of silicon nitride powder, thereby improving the light transmittance of the silicon nitride ceramic slurry and enhancing the mechanical properties of the silicon nitride ceramic.

The invention relates to the technical field of ceramic powder preparation, and discloses high-dispersity AlON powder and a synthesis method thereof and a preparation method of AlON transparent ceramic, and the preparation method comprises the following steps: (1) powder mixing: taking gamma-Al2O3 and a solid carbon source as raw materials, and carrying out ball-milling mixing on the raw materials, an auxiliary agent, a dispersing agent and absolute ethyl alcohol to obtain mixed slurry; (2) drying and sieving: drying, grinding and sieving the mixed slurry to obtain mixed powder; (3) charging and air pressure sintering: charging the mixed powder into a perforated boron nitride crucible, and performing air pressure sintering on the mixed powder in an air pressure sintering furnace to obtain high-dispersity AlON powder; and (4) carbon removal. The AlON powder synthesized by the synthesis method disclosed by the invention is of a nearly spherical single-crystal structure and has good high dispersity.

The utility model relates to the field of air pressure sintering furnaces, in particular to a high-pressure dynamic sealing device for an air pressure sintering furnace door, which comprises a furnace door insulation felt, a soaking barrel end door, a first telescopic assembly and a second telescopic assembly. Even under the condition that the furnace door is closed, the furnace door heat preservation felt can achieve the front-back telescopic function, under the high-temperature working condition, the first telescopic assembly is driven, the first telescopic assembly pushes the furnace door heat preservation felt forwards, the furnace door heat preservation felt and the furnace body heat preservation felt can form a space with better sealing performance together, and therefore the temperature uniformity of a thermal field is improved; and meanwhile, the end door of the soaking barrel can be dynamically stretched out and drawn back, the problem that the heat preservation barrel is broken due to graphite expansion is solved, the product safety is improved, the end opening sealing performance can be constantly kept through dynamic self-adjustment of the end door of the soaking barrel, the temperature uniformity of a thermal field is improved, and therefore the problem that the temperature uniformity of an air pressure sintering furnace is poor is solved.

The present invention discloses a method for preparing a high-thermal-conductivity silicon nitride ceramic toughened with boron nitride, belonging to the technical field of silicon nitride ceramics. The preparation method comprises the following steps: pretreatment of boron nitride fibers, vapor deposition, raw material mixing, compression molding, and gas pressure sintering. The vapor deposition method comprises the following steps: adopting an unbalanced magnetron sputtering method, using a boron carbide target and a magnesium oxide target as target materials to perform vapor deposition on the surface of activated boron nitride fibers. The high-thermal-conductivity silicon nitride ceramic prepared by the present invention can improve its toughness while maintaining its high thermal conductivity. The thermal conductivity of the prepared silicon nitride ceramic is 79.2-81.0 W / (m•K), the flexural strength is 738-745 MPa, and the fracture toughness is 11.3-11.6 MPa•m 1 / 2 , elastic modulus is 263~270GPa, density is 3.09~3.15g / cm 3 .

The invention relates to alpha sialon ceramic taking manganese as stable ions and a preparation method thereof. The alpha-SiAlON ceramic with the manganese as the stable ion is represented by a general formula Mnm / 2Si < 12-m-n > Al < m + n > OnN < 16-n >, m ranges from 1 to 3.6, and n ranges from 0 to 3. The novel alpha-SiAlON ceramic is prepared from Si3N4, AlN, MnO and other powder as raw materials through spark plasma sintering, air pressure sintering or hot pressed sintering and other methods, and the preparation method is simple and convenient. The alpha-SiAlON ceramic taking manganese as stable ions has high hardness and excellent fracture toughness, and is expected to be widely applied to various occasions with relatively high requirements on mechanical properties such as ceramic hardness and toughness.

The invention discloses a high-fracture-toughness silicon nitride ceramic ball and a preparation method thereof, and belongs to the field of high-performance structural ceramic materials. The ceramic ball is prepared by taking high-purity alpha-SiN powder as a matrix and adopting a composite sintering aid system composed of an oxygen-free rare earth compound, aluminum nitride and beta-SiN seed crystal through an air pressure sintering process controlled by program pressure. Under the synergistic effect of the auxiliary system and a specific process, 'bimodal distribution 'beta-SiN columnar crystals and high-melting-point and high-toughness intergranular phases are generated in situ in the material, so that the fracture toughness of the material is remarkably improved on the premise of not sacrificing hardness and strength. The fracture toughness of the silicon nitride ceramic ball is up to 8.5-11.0 MPa.m / , the bending strength is 750-1050 MPa, and the silicon nitride ceramic ball is particularly suitable for precision bearings under high-speed and high-load working conditions, such as a wind power generation main shaft, an aerospace engine main shaft and the like.

This invention relates to the field of structural ceramic materials technology, and discloses a silicon nitride-based composite ceramic material with high fracture toughness and its preparation method. The silicon nitride-based composite ceramic material with high fracture toughness comprises, by mass, the following raw materials: α‑Si3N4 70-82 parts fine powder α‑Si3N4 10-20 parts coarse flour β‑Si3N4 Seed crystals 1-4 parts Y2O3 2 ~5 parts, MgO 0.5~2.0 parts, Al2O3 0 ~1.5 parts. The preparation method includes preparing silicon nitride slurry, preparing silicon nitride composite powder with surface-loaded composite sintering aid, preparing composite particles, preparing ceramic green body, degreasing treatment, and two-stage gas pressure sintering. This invention utilizes... α‑Si3N4 fine powder and α‑Si3N4 The bimodal particle size distribution of coarse powder is beneficial to improving the packing state of raw material powder and enhancing the uniformity during molding and sintering.

The application discloses a kind of silicon nitride ceramic balls and preparation method thereof, its steps are: first with gamma-ammonia propyl triethoxysilane to alpha-silicon nitride powder is modified and is screened 0.1-0.2mm ball seed;With polyvinyl alcohol / carboxymethyl cellulose sodium aqueous solution as binder, rolling forming is obtained in sugar-coated machine silicon nitride ball blank;Again ball blank is placed in by nano silicon nitride and polyacrylic acid ethanol dispersion liquid is prepared by premixing-middle mixing-high speed dispersion enhanced mother liquor, 60-65 ℃ low speed stirring ≥8h complete enhancement;Subsequently 350-500W microwave drying 30-50min, 0.5MPa nitrogen atmosphere 1700-1750 ℃ pressure sintering 4h, finally polishing is obtained high density, high hardness, high wear resistance silicon nitride ceramic ball finished product.Innovatively proposed silicon nitride ball blank mother liquor enhancement technology, using nano silicon nitride sol as mother liquor to ball blank is maintained and enhanced, improve the density, uniformity and strength of ball blank, solve the difficulty that the strength and uniformity of rolling forming ball blank are poor.

Method for producing hard metal bodies that have a hard metal microstructure at room temperature, which is free of tungsten dicarbide and eta phase, in which LPBF, SLM, DMLS or SLS as a laser-based additive manufacturing process with energy input via laser powers of 20 W to 55 W and scan speeds of 20 mm / s to 75 mm / s and track spacings of 30 µm to 205 µm and layer thicknesses of 20 µm to 45 µm at each point of energy input to achieve a temperature of 800 °C to a maximum of < 1800 °C from hard metal granules as starting materials made of WC as a ceramic hard material with Co as a metallic binder phase and an additive of Cr3C2 and the hard metal granules have a porosity of > 0 vol.% to 40 vol.%.-%, a hard metal green body with a density of at least 50% and at most 70% of the theoretical density of the hard metal body is produced, and which is subsequently subjected to sintering at temperatures up to a maximum of 1600 °C, by means of vacuum sintering at temperatures of 1200 to 1600 °C and at partial pressures of 100 to 90000 Pa or gas pressure sintering at temperatures of 1380 to 1600 °C and pressures of 5 to 10 MPa until a density of the hard metal body of ≥ 98% to 99.9% of the theoretical density.

The invention discloses a high-performance carbon nanotube reinforced silicon nitride composite ceramic ball and a preparation method thereof. The method comprises the following steps: firstly, carrying out surface functionalization on carbon nanotubes through acidification, and then realizing highly uniform dispersion of the carbon nanotubes in SiN powder in combination with high-energy ultrasound and planetary ball milling under the protection of inert gas; then carrying out spray granulation, mould pressing and cold isostatic pressing to obtain a high-density biscuit; carrying out degreasing, air pressure sintering and hot isostatic pressing post-treatment to obtain an almost fully-dense composite material; and finally, the high-precision ceramic ball is obtained through precise grinding. According to the preparation method disclosed by the invention, through a combined sintering process of chemical-physical-mechanical synergistic dispersion and air pressure sintering-hot isostatic pressing, the problems that the carbon nanotubes are easy to agglomerate and the interface is combined and controlled are effectively solved, and the prepared composite ceramic ball has high toughness (greater than or equal to 7.5 MPa.m / ), high reliability (the Weibull modulus is greater than or equal to 15) and long fatigue life; the method is suitable for the high-end equipment manufacturing field.

The invention belongs to the technical field of ceramic material preparation, and provides a high-thermal-conductivity silicon nitride ceramic substrate and a preparation method thereof. According to the method, a high-entropy oxide sintering aid is prepared through a coprecipitation calcination method, titanium hybrid polycarbosilane is chemically synthesized to serve as a functional aid, and meanwhile silicon nitride powder is subjected to surface coating modification; the preparation method comprises the following steps: uniformly mixing modified silicon nitride powder with the two assistants, carrying out tape casting to obtain a biscuit, carrying out multi-stage air pressure sintering on the biscuit, regulating and controlling atmosphere, pressure and temperature in a sintering procedure, completing low-temperature treatment, vacuum sintering, high-pressure densification and high-temperature and high-pressure sintering step by step, and carrying out specific annealing treatment in a cooling stage to obtain the silicon nitride ceramic. According to the invention, by utilizing the synergistic effect of the compound additive and a precise sintering schedule, the growth of silicon nitride grains is effectively promoted, and the grain boundary phase is optimized, so that the prepared silicon nitride ceramic substrate is highly compact in structure and pure in grain boundary, and excellent heat-conducting property is realized.

The invention discloses a low-temperature normal-pressure sintering preparation method of silicon nitride ceramic for a high-power electric heating element, which comprises the following steps: (1) mixing silicon nitride powder and a nitride glass sintering aid, based on the total weight of the mixed raw materials, the use amount of the silicon nitride powder is 60-93%, and the use amount of the nitride glass sintering aid is 7-40%; (2) drying the mixture obtained in the step (1) to obtain a dried material; (3) molding the dried material obtained in the step (2) to obtain a molded material; and (4) carrying out normal-pressure sintering on the formed material obtained in the step (3). According to the method disclosed by the invention, the nitride glass sintering aid is adopted, and the sintering temperature is reduced to a low-temperature interval of 1550-1680 DEG C, so that the dependence on expensive and complex hot-pressing or air-pressure sintering equipment is eliminated, the energy consumption and the cost are remarkably reduced, meanwhile, the normal-pressure sintering of the high-performance silicon nitride ceramic is realized, and a process foundation is laid for large-scale and low-cost manufacturing.

The invention discloses a silicon nitride ceramic ball and a preparation method thereof. The preparation method comprises the following steps: mixing a modifier gamma-aminopropyltriethoxysilane with alpha-silicon nitride powder, and stirring for 5-10 minutes to obtain modified silicon nitride powder; the modified silicon nitride powder is pressed into a compact block in an isostatic press, then the block is crushed into small particles with the diameter of 0.1-0.2 mm, and the small particles are ball seeds; preparing a binder glue solution from polyvinyl butyral and polysilazane; the modified silicon nitride powder and the ball seeds are put into a sugar coating machine for rolling forming, the binder glue solution is sprayed to the surfaces of the balls through a spraying device in the rolling process, and silicon nitride ball blanks can be obtained after rolling forming is conducted for a certain time; putting the silicon nitride ball blank into a microwave drying oven and drying at specific power; putting the dried silicon nitride ball blank into an air pressure sintering furnace, and sintering for a period of time at a specific temperature to obtain a silicon nitride ceramic ball; and polishing the sintered silicon nitride ball to obtain a silicon nitride ceramic ball finished product.

The invention relates to the technical field of air pressure sintering furnaces, and aims at providing a rotary material table air pressure sintering furnace which comprises a high-pressure furnace body, a furnace cover, a magnetic drive rotating device, a rotating shaft, a rotary material table and a heat preservation structure. The magnetic driving rotating device drives the rotating shaft to drive the rotating material table to rotate at a constant speed, so that materials are uniformly treated; the rotating shaft adopts a sectional structure, a high-temperature section is made of a C-C composite material, and a low-temperature section is made of a water-cooling stainless steel material; the heat preservation structure is a double C-C composite material heat insulation assembly, and efficient heat preservation is achieved; the high-pressure furnace body is provided with a heating element, a thermocouple, a mass flow meter and a precise pressure valve, and precise regulation and control of temperature, pressure and atmosphere are achieved. The problems that a traditional air pressure furnace is uneven in material treatment, poor in high-temperature and high-pressure resistance and low in parameter control precision are solved, the material treatment quality is improved, and the air pressure furnace can be widely applied to the fields of ceramic material sintering, hard alloy preparation and the like and has high practical value and popularization prospects.

This invention relates to the field of high-performance structural ceramic materials and their corrosion resistance optimization technology, and particularly to a method for preparing high-performance silicon nitride ceramics. Performance improvement is achieved through dynamic optimization of composite sintering aids, closed-loop control of gas pressure sintering, and multi-process data linkage. In the raw material pretreatment stage, a laser particle size analyzer is used to monitor particle size distribution in real time, and surface modification parameters are adjusted accordingly to form a uniform monomolecular coating layer. The ratio of rare earth oxides to alumina in the composite sintering aids is dynamically adjusted according to the mixing torque fluctuations to suppress agglomeration and segregation of the aids. In the gas pressure sintering stage, the argon pressure and heating rate are dynamically adjusted based on the slope of the shrinkage curve, combined with low-temperature nitrogen protection and high-temperature argon densification to promote the directional alignment of β-phase grains. Multi-dimensional process control synergistically optimizes grain boundary composition, structure, and density, significantly improving the corrosion resistance and service life of silicon nitride ceramics in sulfur-containing environments.

The invention relates to the technical field of ceramic-based composite materials, in particular to a low-expansion high-thermal-conductivity high-mechanical-property silicon carbide composite material and a preparation method thereof. The low-expansion high-thermal-conductivity high-mechanical-property silicon carbide composite material is prepared from the following raw materials in percentage by mass: 35 to 50 percent of silicon carbide, 15 to 60 percent of cordierite, 4 to 25 percent of beta-spodumene, 0 to 5 percent of low-temperature oxide powder and 0 to 15 percent of fused quartz. The thermal expansion behavior of the material is regulated and controlled through the multi-component synergistic effect, meanwhile, the microstructure is optimized through the air pressure sintering technology, and the finally prepared silicon carbide composite material has good thermal expansion performance, heat conduction performance and mechanical performance.

The invention discloses a kind of preparation technology and preparation system based on silicon nitride ceramic bearing ball, relate to silicon nitride ceramic bearing ball technical field, comprise the following steps: S1, raw material mixing: adopt wet ball milling to mix high-purity silicon nitride powder, sintering aid and toughening agent to obtain compound A;S2, dry pressing molding: compound A is extruded, so that compound A forms a blank;S3, gas pressure sintering: under nitrogen atmosphere, blank is rapidly heated to 1800 DEG C, heat preservation 15 35min, then heat preservation more than 8 hours after being cooled to 1600 DEG C, to suppress grain growth, obtain fine grain structure. The present invention can effectively improve the density distribution inside silicon nitride ceramic bearing ball, by density uniform so that silicon nitride ceramic bearing ball is more stable when rotating at high speed, reduces imbalance phenomenon, greatly improves the stability of bearing when rotating at high speed.

The invention relates to the technical field of ceramic materials, in particular to aluminum oxide ceramic and a preparation method thereof. The aluminum oxide ceramic provided by the invention is prepared by drying a ceramic biscuit and then carrying out air pressure sintering, the ceramic biscuit is prepared by pressing alumina powder with D50 of 0.35 to 0.45 [mu] m; the initial vacuum degree of air pressure sintering is within 10 Pa, the temperature rise rate of sintering is 2-3 DEG C / min, and the highest sintering temperature does not exceed 1600 DEG C; after the temperature is increased to the highest sintering temperature, the pressure is increased to 2-3 MPa, and heat preservation is conducted for 1-2 h. Compared with the alumina ceramic prepared under the traditional oxidation pressureless sintering condition, the alumina ceramic provided by the invention is higher in compactness, higher in volume density and better in mechanical property, the bending strength is improved by 41.6%, the alumina ceramic can be used in worse working conditions, and the alumina ceramic has the characteristic of longer service life.

The application belongs to the technical field of silicon carbide ceramic preparation, and particularly relates to a silicon carbide ceramic slurry based on DIW-3D printing, a silicon carbide ceramic product and a preparation method. The silicon carbide ceramic slurry is prepared from raw materials including the following components and weight contents: silicon carbide mixed powder 60-100 parts, thermosetting resin 10-40 parts, dispersing agent 5-15 parts and thermal initiator 0.01-1 part. The application realizes the application of DIW-3D printing in the preparation of silicon carbide ceramic through the synergistic effect of double-particle-size SiC grading, introduction of B4C sintering aid, special resin and dispersant system, thermal initiation and solidification, DIW rheological design and gas pressure sintering, saves the material cost in the manufacturing process, prepares a silicon carbide sample with excellent mechanical properties, and further widens the development of silicon carbide ceramic.

The application relates to the field of semiconductor packaging and discloses a gas pressure pressure sintering method for carrier brazing, which comprises the following steps: loading, loading a product shell into a bearing clamp and introducing the product shell into a chip mounter; full-automatic mounting, controlling a dispensing head, prepositioning first-layer flux in a dispensing form to a carrier mounting position and placing a preformed soldering sheet above the first-layer flux; again controlling the dispensing head in the chip mounter, prepositioning second-layer flux in a dispensing form to a preformed soldering sheet mounting position, and placing a carrier above the second-layer flux for preliminary positioning; unloading, after the mounting is completed, conveying the clamp together with the carrier to be sintered out of the outside of the chip mounter by the chip mounter; and gas pressure pressure curing, placing the mounted preformed soldering sheet and the carrier together with the bearing clamp into a gas pressure pressure oven for pressure curing. Compared with traditional clamp physical pressure, the application has the advantages of lower operation difficulty, higher position precision, lower soldering cavity rate and higher sintering reliability.